Heating furnace



April 18, 1944. w TQRR 2,346,876

HEATING FURNACE Filed March 1, 1941- INVENTOR Mammy-W 70/7 BY OM9*MW.

ATTORNEYS.

Patented Apr. 18, 1944 HEATING FURNACE Thomas W. 'lorr, Dowagiac, Mich., assignor to Rudy Furnace Company, Dowagiac, Mich a corporation of Michigan Application March 1, 1941, Serial No. 381,307 6 Claims. (cries-11s) This invention relates to inrn'irovements in heating furnaces.

The main objects of my invention are:

First, to provide a warm air furnace of steel construction which is substantially free from hot spots in the radiating surface thereon, the latter being maintained at a practically uniform temperature throughout its surface and thereby giving a more emcient delivery or transfer of heat to the air stream passing the outer surface thereof.

Second, to provide a steel furnace of the character described wherein by reason of the uniformity of distribution of heat to the radiating surface thereof the noises generally accompanying expansion and contraction in steel furnace construction are substantially eliminated.

Third, to provide an equalized heat distribution construction for awarm air furnace wherein the heat evolved is prevented from passing in a direct and rapid stream to the fluid outlet, thereby providing for a long hold-over of heat in the furnace and preventing a condition wherein the furnace is permitted to cool below the desired temperature in its intermittent operation, this condition being sometimes referred to as cold '70s, thus enabling frequent fan operations after the burner is shut oil. and maintaining greater fuel economy.

Fourth, to provide a steel furnace of the type described wherein the total required radiator surface for a given heat input is substantially decreased thereby compacting the furnace as a whole, and in which the said surface is uniformly heated at a relatively low temperature throughout the entire surface thereof, with resultant improvement or increase inefficiency.

Fifth, to provide an oil burning furnace of the type described which operates at high efliciency regardless of the input of oil fed thereto or the capacity of nozzle utilized to thereby provide a furnace of widely variable output or capacity with uniformly high emciency.

.Sixth, to provide an oil burning furnace of the character described which is free from fluttering or. pulsations at the commencement of operation thereof regardless of the'back pressure thereon.

Further objects relating to details and economics of my invention will appear from the deillustrating a furnace in accordance with my invention, the details of the equalized hea't dis-. tribution and radiating structure being conventionally indicated in dottedlines to show the relative positioning thereof in the furnace shell or casing.

Fig. 2 is a fragmentary view in front elevation partially broken away and in verticalsection, the furnace casing being largely removed, illustrating the construction and relation of the radiating surface and the heat distributing structure associated with the combustion chamber of the furnace in accordance with my invention.

Fig. 3 is a fragmentary top plan view, being partially broken away and in section on line 3-3 of Fig. 2, further illustrating the relation of the parts. 1

Referring to the drawing, reference numeral i indicates a suitable rectangular furnace casing having opposed sidewalls and front and rear walls surrounding the heat generating, distributing and radiating structure of my furnace, which structure is generally indicated by reference numeral 2. The latter includes as the outer element thereof the upright rectangular steel radiator shell 3 which is practically coextensive in height with the furnace and is closed at its top.

This shell is separated from the furnace casin l by an air circulating space 4 communicating with the interior of the dome 5 forthe casing into which the various hot air ducts 6 are led. The shell-3 includes a removable front plate 5 bolted thereon and readily removable for access to the remainder of the parts disposed interiorly of the shel As illustrated in Fig. 2, the radiator shell 3 has secured thereo at the side thereof a plurality of braces 26 which hold in place a refractory combustion chamber 1 in which the oil burner unit 8 is disposed, see Fig.1. this unit being supplied with suitable connections 9.

The braces 26 furtherserve' as supports for a primary elongated rectangular steel equalizer member U) which extends for 'asubstantial distance above the braces vertically-in the radiator shell 3, being spaced a substantial'distance from the four sides thereof. g

. Telescopingly surrounding the-aforesaidequalizer member l'cfand sustained on theshell 3 by scription to follow. The invention is defined in Ineans of brackets II, and likewise secured to the claims.

A structure embodying thefeaturesof my in.- vention' is. illustrated in the accompanying draw ing, wherein:

Fig. 1 a fragmentary view inside elevation the equalizer member by thef urtlierl'fbrackets I2, is the secondary equalizer member f it whichis of steel in rectangular sectional outlinalclosed at its top. This'secondary egualiz'er'is in ertedover theequali'zrmcm Lexi i stantial distance downwardly lengthwise toward the bottom of the latter.

The aforesaid construction provides a relatively lengthy and tortuous path for the products of combustion from oil burner 8. They must first rise up through the primary equalizer member ID transferring heat thereto and being distributed around its perimeter, then travel downwardly all around the space surrounding the said member between the same and the secondary equalizer member 13. This effects a substantial and uniform distribution of the hot products of combustion and the transferred heat units. Following the aforesaid downward travel, the products of combustion must travel upwardly through the space surrounding the secondary member l3 between the same and the radiator shell 3 on the side of the shell 3 opposite from the flue ll, there being an opposite movement downward of the burned gases between the equalizer member l3 and the shell 3 on the side of the shell 3 in which the opening to flue I4 is located. This furthers and completes the distribution of heat in uniform manner over the inner surface of the radiator shell 3. Heating units are picked up from the latter by air circulated past the outer surface thereof in space 2 by a fan (not shown).

Subsequent to traversing the inner walls of the radiator shell 3, the products of combustion pass outwardly through a flue ll disposed at a relatively low point in the shell into a heat exchanger |5 disposed behind the radiator shell, thence outwardly from the furnace casing through the flue IE to the stack.

In the operation of the foregoing furnace construction all intensely hot spots on the radiating surface or shell 3 have been eliminated. At the same time, portions of this surface which would ordinarily be of lower temperature than the heat equalizer members l0, l3 so spread the heat over the entire surface of the radiator shell by reason of its dissemination in circulating through the equalizers that it is held at a practically uniform temperature, thereby giving amuch more efficient delivery of heat into the air stream circulating between the said shell and the furnace casing I. This obviates the excessive and noisy the air stream will be so transferred uniformly at all points at which the stream impinges the radiator shell and, moreover, at a relatively low temperature in the interests of efficiency of transfer.. I consider that it is in this respect that my system distinguishes primarily from previous efforts in this art. Perhaps it is because of this distinguishing feature that the economy of construction and simplicity of the herein described furnace results. All previous attempts to increase the efficiency of heat transfer by air circulation past radiating surfaces, for example, in the use of a number of small tubes heated interiorly by combustion gases and having air circulating, around them, or employing means for. circulating air on one side of the number of furnace pipes on the opposite side of which the flue gas is caused to flow; are uniformly complicated and expensive in construction. This can certainly not be said of the present design.

A prominent characteristic of the flue gas heat equalizer furnace which I have described is the slowness with which the heat is passed through the outer radiating surface or shell with resultant maintenance of the air stream externally of the shell at a satisfactory temperature for a substantial period of the time after the burner has been shut off. Cold 70's are eliminated, an end that every manufacturer of steel furnances has attempted to achieve. Due to this equal distribution of heat by the equalizer member, the stack temperature goes up very slowly and, for the same reason, drops very slowly after the burner is shut off. This slow and even rise and fall of the stack temperature I find establishes a very definite relation between stack temperature and the temperature in the warm duct. There is a ratio of approximately one to seven between the duct temperature and the stack temperature, i. e., when the furnace is in normal operation for average winter weather, which presumes expansion and contraction which have heretothose in which air passes over the hot surfaces,

the radiating surfaces are very much more efficient at temperatures around 400 or 500 than they are at higher temperatures of 700 or 800.

I desire to emphasize the fact that in my construction neither one of the equalizer members l0, i3 is located in the air stream. These equalizers are not merely for the purpose of deflecting or directing the flow of.gases, but, more deflnitely, they are decidedly for the purpose of equalizing and distributing the temperature over the inside of the enclosing radiating shell therefor, which latter is adjacent an external air stream, to the end that the heat which is transferred to that the burner will be on half the time and off half the time at more or less regular intervals. If the temperature of the stack rises seven degrees, there will be a rise of one degree in the temperature of the air in the warm air duct. When there is a drop of seven degrees, there will be a drop of one degree. As an example, derived from the operation of a furnace as described, with an operation of the burnerover a period of several hours varying from seven to nine minutes at a time, and an foif time of the burner varying from eight and a half to nine minutes, an average stack temperature during the on operation of the burner is about 468 with a duct temperature averaging 145. During the off" period of the burner, the stack temperature receded to an average temperature of 295 and the average duct temperature is v This means that the present design accomplishes a very desirable result by a very simple construction, in that, without the use of a twospeed fan or a high and low burner arrangement there is provided in an average winter weather a continuous fan operation with a very slight variation in duct temperature, maintaining a uniform temperature in a heated room supplied by the furnace.

Another advantage of the structure of the present invention is the range of capacity which is made possible without affecting in a' material manner the efllciency of operation. Thus, the operation described in the preceding paragraphs was obtained with a 1.35 gallon nozzle. With a 1 gallon nozzle, the only change resulting is an characterizing the same.

approximately 25 reduction in stack temperature during the operation of the burner. The efficiency is not affected more than one or two per cent, which, owing to the high inherent efficiency nace is in its complete elimination of pulsations I This is one of the fac-.

during initial operation. tors which has seriously annoyed the furnace designer and is still a source of trouble to manupossible by the above described'equalizer radiatorconstruction, in addition "to the equalization of heat] distribution and enhanced efficiency A still further advantageous of the burner itself, is negligible. A wide input 5 facturers, At the commencement of operation range is available adapting a furnace for varying of many oil furnaces, when the latter are cold, installation or demand, which is a great advanthere is apt to be a flutter or pulsation until the tage to the dealer in reducing the variety of his furnace becomes warm. If the flue conditions are stock for one size furnace will suflice for a great such that there is any back pressure at all-on the majority of his installations, ranging from 8- l0 furnace, such pulsations are sure to result, in room houses up to 12 or 14 rooms. 7 more or less aggravated degree. I have found Tests comparing the performance of the equalthat a furnace as described above, due to its uniized furnace structure described above with other form equalized distribution of and transfer of types now on the market illustrate clearly the heat to the air, can be operated with as much as enhanced efliciency of the former, likewise the lo 1 6 inch back pressure without any tendency fact that for a given heat input the required whatevertopulsate. radiating surface is substantially decreased, While the structure illustrated is an embodithereby satisfying a pronounced recent trend in ment of my invention in an oil burning furnace, the design of furnaces of smaller size. There is a it will be understood that it is as .well adapted for substantial demand on the part of the public for use in a gas burning furnace and is further desmaller furnaces occupying less space in a basesirable for use with solid fuel, although of parment. ticuiar m'erit withgas or liquid fuel.

In the aforesaid tests three furnaces were used. I have illustrated and described the features of Furnace A was of the cast iron, direct heating my invention in an embodiment which is very radiator type in which the flue gases are caused practicah I have not attempted to illustrate or to travel vertically being horizontally baiiled durdescribeother embodiments or adaptations as it ing the travel, and in which the air is'circulated is believed this disclosure will enable those skilled directly over the outer radiating surface of the in the art to embody or adapt my invention as element. This furnace had a heat input of-80,000 desired.

B. t. u. and requires 49 sq. ft. of radiating surface. Having thus described my invention, what I Furnace B was a steel tube, direct radiation type claim as new and desire to secure by Letters Pathaving'a 65,000 B. t. u. input and in which the ent,is:

flue gases are circulated vertically through a plu- 1. An oil burning furnace of steel construction rality of steel spaced tubes with the air to be comprising an elongated vertical steel radiator heated in direct external contact with the tubes. shell providing a heat radiating surface of sub- The requisite heating surface of this furnace is stantial area, said shell being substantially co- 29.6 sq. ft. Furnace C was a heat equalizer type extensive in height with the furnace, a plurality in full accordance with the foregoing disclosure of brackets mounted interiorly of said shell, said with a heat input of 65,000 B. t. u.,-which howradiator shell having a refractory combustion ever required but 20 sq. ft. of radiatingsurface. 40 chamber disposed therein at the base thereof and The operating data of the above three furnaces positioned by said brackets; said ,combustion are set forth, for purposes of clarity, in tabulated chamber having an oil burner therein, a, first form in the following chart, in which the radiathollow open ended steel equalizer member ioing surface of furnace A has been expressed twice, cated centrally in said shell above said combusi. e., for its actual 80,000 B. t. 11. input and for a tion chamber and supported on said brackets, said theoretical input equal to the heat input of the member extending vertically for a. substanti l other two furnaces tested. a distance in said shell and directing products of B.t.u. B. t. u Net Sq. ft. heat input Per cent saving Style heat stack radiating per sq. ft. inradiating input temp. surface radiating surface surface I Degrees A-Cast iron direct radiation gm 475 1,633 B-Steel tube direct radiation 65, 000 475 29.6 2,200 25.6 over-A C-Equalizertype 65,000 475 20 3,250 47.2 overA (32.4 over B) Compa in -t p rman e of th f re ing o0 combustion from said burner upwardly in the three types of heatin l m tai i s en that shell, a second hollow stee1 equalizer member while furnace B, s compared w furnace having a closed top in spaced relation to the top effects a saving of 25.6% in radiating surface reof the first member andvertically extending sides quired, the equalizer type furnace C involves a of substantial length telescopingly associated saving of 32.4% over furnace Band 47.2% oyer 5 with said first member with the sides of said memfurnace A. bers overlapping one another for a substantial In these comparative tests all conditions of verticaldistance and laterally spaced from one room temperature, firing, etc., were similar.- The another, said second member terminating short results clearly indicate that substantial saving in oi the bottom of the first member and being cost of material and overall dimension is made spaced'substantially from the sides of said shell to define an annular, vertically elongated down.-

ward path for the circulation of products'of combustion between said members and an-annular,

' *verticaliy elongated upward and downward paths feature of my fur- 7| between said second member and radiator shell whereby the heat from the products of combustion is substantially equalized in intensity and distributed over the annular inner surface of said shell following its circulating movement, through the members, said shell having a flue opening disposed substantially on a level with the lower end of said second equalizer member, a heat exchanger having N vertically spaced flue openings, the lower of which is connected to said flue opening in the shell and the upper of which is for exit of burned gases therefrom and a furnace casing surrounding and enclosing said shell and heat exchanger to define an air space surrounding the latter for the circulation of 'air over the external surface only of the shell and heat exchanger to efiect transfer of heat from the shell thereto, the space interiorly of said shell and heat exchanger circulating products of combustion exclusively.

2. A furnace construction comprising an elongated vertical steel radiator shell providing a heat radiating surface of substantial area, said shell being substantially coextensive in height with the furnace, said radiator shell having a refractory combustion chamber disposed therein at the base thereof, said combustion chamber having a heat generating device therein, a first hollow open ended steel equalizer member located centrally in said shell above said combustion chamber, said member extending vertically for a substantial distance in said shell and directing products of combustion from said device upwardly in the shell, a second hollow steel equalizer member having a closed top in spaced relation to the top of the first member and vertically extending sides of substantial length telescopingly associated with said first member with the sides of said members overlapping one another for'a substantial vertical distance and laterally spaced from one another, said second member terminating short of the bottom of the first member and being spaced substantially from the sides of said shell to define an annular, vertically elongated downward path for the circulation of products of combustion between said members and an annular, vertically elongated upward and downward paths between said second member and radiator shell whereby the heat from the products of combustion is substantially equalized in intensity and distributed over the annular inner surface of said shell following its circulating movement, through the members, said shell having a flue opening disposed substantially on a level with the lower end of said second equalizer member, a heat exchanger having vertically spaced flue openings, the lower of which is connected to said flue opening in the shell and the upper of which is for exit of burned gases therefrom and a furnace casing surrounding and enclosing said shell and heat exchanger to define an air space surrounding the latter for the circulation of air over the external surface only of the shell and heat exchanger to effect transfer of heat from the shell thereto, the space interiorly of said shell and heat exchanger circulating products of combustion exclusively.

3. A furnace construction comprising an elongated vertical radiator shell providing a heat radiating surface of substantial area, said shell being substantially coextensive in height with the furnace, said radiator shell having a refractory combustion chamber disposed therein, said combustion chamber having a heat generating device therein, a first hollow open ended equalizer member located centrally in said shell above said combustion chamber, said member extending vertically for a substantial distance in said shell and directing products of combustion from said deviceupwardly in the shell, a second hollow equalizer member having a closed top in spaced relation to the top of the first member and vertically extending sides of substantial length tele scopingly associated with said first member with the sides of said'members overlapping one another for a substantial vertical distance and laterally spaced from one another, said second member terminating short of the bottom of the first member and being spaced substantially from the sides of said shell to define an annular, vertically elongated downward path for the circulation of products of combustion between said members and an annular, vertically elongated upward and downward paths between said second member and radiator shell whereby the heat from the products of combustion is substantially equalized in intensity and distributed over the annular inner surface of said shell following its circulating movement, through the members, said shell having a flue opening disposed substantially on a level with the lower end of said second equalizer member, a heat exchanger having vertically spaced flue openings, the lower of which is connected to said flue opening in the shell and the upper of which is for exit of burned gases therefrom and a furnace casing surrounding and enclosing said shell and heat exchanger for the circulation of air to be heated thereover.

4. An oil burning furnace of the type described, comprising a combustion chamber, a first hollow, vertically extending, open ended equalizer member disposed concentrically of said chamber and in communication therewith, said member extending for a substantial distance vertically of the furnace, to circulate products of combustion upwardly from the chamber, a second equalizer member having a closed top in vertically spaced relation to the top of the first member, said second member surrounding said first member and terminating adjacent but short of the bottom thereof with a substantial vertical overlap of the walls of the members to provide an annular passage of substantial circumference and lengthJor the circulation of products of combustion downwards from the top of said first member, and a radiator shell surrounding and encasing said members and combustion chamber in spaced relation thereto, said shell providing an annular passage of substantial circumference and vertical height between said second equalizer member and the shell for the circulation of products of combustion passing around the lower end of the second member, said first and second equalizer members uniformly distributing annularly the heat of tle products of combustion during circulation thereof whereby the heating units are uniformly transferred to the inner surface of said shell, said shell having a flue opening disposed substantially on a level with the lower end of said second equalizer member, a heat exchanger having vertically spaced flue openings, the lower of which is connected to the flue open: ing in the shell and the upper of which is for exit of products of combustion, and a furnace per portion having an unobstructed discharge at an intermediate member closed at its upper end and disposed in embracing concentric relation to said upper portion of said combustion chamber to receive the heated gases and products of combustion discharged from the top of said combustion chamber and ccacting therewith to provide an annular down-flow space surrounding said upper portion of said combustion chamber, the capacity of said space being such that normally the heated gases and products of combustion travel in a uniform downward flow around the combustion chamber to be discharged at the lower end of said intermediate member, a radiator shell sealed against admission of external air disposed in concentric embracing relation to said intermediate member to receive the heated gases and products of combustion discharged from the lower end thereof, the capacity of the space between said intermediate member and radiator shell being such as to insure a substantially uniform distribution of the heated gases and products of combustion throughout the space as they flow upwardly and downwardly therein, said shell having a flue opening therein disposed substantially on a level with the lower end of said intermediate member, and a hot air casing surrounding said radiator shell.

6. In a heating furnace, the combination of a combustion chamber including an upright upthe top thereof, an intermediate member closed at its upper nd and disposed in embracing concentric relation to said upper portion of said combustion chamber to receive the heated gases and products of combustion discharged from the top of said combustion chamber and coasting therewith to provide an annular down-flow space surrounding said upper portion of said combustion chamber, the capacity of said space being such that normally the heated gases and products of combustion travel in a uniform downward flow around the combustion chamber to be discharged at the lower end of said intermediate member, a radiator shell disposed in concentric embracing relation to said intermediate member to receive the heated gases and products of combustion discharged from the lower end thereof, the capacity of the space between said intermediate member and radiator shell being such as to. insure a substantially uniform distribution of the heated gases and products of combustion throughout the space as they flow upwardly and downwardly therein, said shell having a flue opening therein disposed substantially on a level with the lower end of said intermediate member, and a hot air casing surrounding said radiator shell. I

THOMAS W. TORR. 

